1. Field of the Invention
The present invention relates to an apparatus for recording images on a recording sheet, such as paper, by allowing recording particles to jump and directly attach to the recording sheet.
2. Description of the Related Art
The U.S. Pat. No. 5,477,250 issued on Dec. 19, 1995 discloses a recording apparatus. This recording apparatus comprises a cylindrical toner retaining member, which is rotatable, for retaining charged toner particles (recording particles) on its outer peripheral surface, and a back electrode spaced from the toner retaining member. The back electrode is electrically connected to a power source, and an electric field is formed to attract the charged toner particles on the toner retaining member toward the back electrode. An insulating plate provided with a plurality of apertures, through which the toner particles can pass, is disposed between the toner retaining member and the back electrode. In addition, the insulating plate is provided with a ring-shaped electrode surrounding each of the apertures.
In the above-mentioned recording apparatus, when a signal corresponding to image data is applied to the electrode, the toner particles existing in a position on the toner retaining member opposed to the electrode separate and jump into the corresponding aperture. After passing through this aperture, the toner particles attach to a recording sheet, and an image corresponding to the image data is recorded on the recording sheet.
In the above-mentioned recording apparatus, however, the plurality of apertures in the insulating plate are slightly shifted from one another in the rotation direction of the toner retaining member in some cases in order to raise resolution. In such cases, when two apertures adjacent to each other are viewed in the rotation direction of the toner retaining member, if the ring-shaped electrodes formed around each aperture are positioned so as to overlap with each other although the two ring-shaped electrodes do not make contact with each other, an area on the toner retaining member, wherein the toner particles jumping to one of the apertures located on the upstream side in the rotation direction of the toner retaining member have been retained, may partially overlap with an area on the toner retaining member, wherein the toner particles jumping to the other aperture located on the downstream side thereof. As a result, the amount of the toner particles passing through the other aperture located on the downstream side is less than the amount of the toner particles passing through the aperture located on the upstream side. Consequently, streak-like unevenness in image density may occur on an image to be formed.
To eliminate such unevenness in density, a measure of rotating the toner retaining member at high speed can be used. However, this measure is not desirable since the toner particles become heated, thereby causing another problem of fusing and adhering of the toner particles on the toner retaining member.